Vitreous glass seal beam lamp units have been used for vehicle lighting since at least as early as the 1930's in the United States, These lamps include a parabolic reflector having a highly mirrorized inner surface that usually has two openings in the base portion that receive connectors for a filament aligned within the reflector. The reflector is enclosed by a circular convex lens also constructed of glass that is located with respect to the reflector by various types of integral locating tabs and is fused to the reflector by heat fusion. The connector assemblies are also connected to the reflector by a heat fusion process, and the content and pressure of gas within the reflector-lens envelope is carefully controlled through a filling tube formed integrally with the rear of the reflector that is fused after the evacuation and/or inert gas filling of the lamp envelope.
Such a seal beam lamp unit is shown and described in the D. K. Right U.S. Pat. No. 2,148,314 dated Feb. 21, 1939.
These seal beam lamp units, which by themselves are replaceable after the filaments burn out, require complicated locking rings and adjustment assemblies permanently carried by the associated vehicle to hold the lamp units in proper position. The locking rings frequently include adjusting brackets for varying the attitude of the lamp unit to properly direct the lamp's beam to effect the desired lamp alignment.
These prior mounting arrangements and also the lamp units themselves, do not have any provision for shock-mounting the lamp or lamp filaments and efforts to devise them to attain shock-absorbing characteristics have been largely unsuccessful without eliminating the beam adjustment function of the mount.
With the advent of rectangular seal beam lamp units, a shock-absorbing mount has been devised for a seal beam lamp that completely shock-mounts the lamp while at the same time permits limited attitude adjustments of the lamp's beam, namely a shock-absorbing mount for a rectangular seal beam lamp shown in the inventor's co-pending application Ser. No. 148,698 filed May 12, 1980 now U.S. Pat. No. 4,345,307 entitled "Rectangular Headlamp Retainer" assigned to the assignee of the present invention. Even this mount, however, is quite costly and therefore forms a part of the vehicle itself and is not replaced at lamp burnout with the seal beam lamp unit itself.
It has been suggested that the reflector of a rectangular seal beam lamp be constructed of a plastic material and that support flanges be formed integrally with the plastic material to eliminate the complicated mounting flanges and rings required in prior lamp units. Such a construction is shown in the Thomas T. Talon et al U.S. Pat. No. 4,188,655. This patent discloses three integral flanges on a plastic reflector that cooperate with three adjusting assemblies mounted to the vehicle that permit adjustment of the lamp beam in two orthogonal planes. While such an arrangement is suitable for many passenger automobile applications, it remains quite costly because of the three separate adjusting mechanisms required, and it does not provide for, nor can it accommodate any known effective shock-absorbing mechanism.
It is a primary object of the present invention to provide a simplified replaceable seal beam lamp and support unit for utility vehicles that does not have the problems and disadvantages noted above in prior art seal beam lamp units.